orderedPosterizeImage

Performs an ordered dither based on a number of pre-defined dithering threshold maps,
but over multiple intensity levels, which can be different for different channels,
according to the input arguments. Available since 6.3.1

For example: "o3x3,6" generates a 6 level posterization of the image with a ordered 3x3 diffused pixel dither being applied between each level. While checker,8,8,4 will produce a 332 colormaped image with only a single checkerboard hash pattern (50 grey) between each color level, to basically double the number of color levels with a bare minimim of dithering. ¯\_(ツ)_/¯

The predefined posterization types available are defined in the ImageMagick file: config/thresholds.xml

Performs an ordered dither based on a number of pre-defined dithering threshold maps,
but over multiple intensity levels, which can be different for different channels,
according to the input arguments. Available since 6.3.1

For example: "o3x3,6" generates a 6 level posterization of the image with a ordered 3x3 diffused pixel dither being applied between each level. While checker,8,8,4 will produce a 332 colormaped image with only a single checkerboard hash pattern (50 grey) between each color level, to basically double the number of color levels with a bare minimim of dithering. ¯\_(ツ)_/¯

The predefined posterization types available are defined in the ImageMagick file: config/thresholds.xml

Parameters

threshold_map

string

A string containing the name of the threshold dither map to use

channel

int

Provide any channel constant that is valid for your channel mode. To
apply to more than one channel, combine channeltype constants using
bitwise operators. Refer to this
list of channel constants.